This invention relates to electrophoretic information displays (EPID) in general and more particularly to an EPID display employing a mesh like electrode.
The prior art is replete with a number of various patents and articles concerning electrophoretic displays. Such electrophoretic displays have been widely described and disclosed in the prior art, and essentially the assignee herein, namely--Copytele, Inc. of Huntington Station, N.Y., has recently developed an electrophoretic display which has an image area of approximately 11.times.81/2 inches and is designed to be used either as a separate display or to be combined with other displays. The company has the ability to combine as many as four such displays to create image areas as large as approximately 22.times.17 inches.
The information on such displays can be changed either locally or remotely and can be viewed at an angle of nearly 180.degree.. Such displays have extremely high resolution and can accommodate over 160,000 pixels within an image area of approximately 2.8 inches diagonally. In regard to such displays, reference is made to U.S. Pat. No. 4,655,897 issued on Apr. 7, 1987 entitled ELECTROPHORETIC DISPLAY PANELS AND ASSOCIATED METHODS to Frank J. DiSanto and Denis A. Krusos and assigned to Copytele, Inc., the assignee herein.
In that patent there is described an electrophoretic display panel which includes a planar transparent member having disposed on a surface a plurality of vertical conductive lines to form a grid of lines in the Y direction. On top of the grid of vertical lines there is disposed a plurality of horizontal lines which are positioned above the vertical lines and insulated therefrom by a thin insulating layer at each of the intersection points. Spaced above the horizontal and vertical line pattern is a conductive plate. The space between the conductive plate and the X and Y line pattern is filled with an electrophoretic dispersion containing chargeable pigment particles.
When a voltage is impressed on the X and Y lines, pigment particles which are located in wells or depressions between the X and Y pattern are caused to migrate towards the conductive plate and are deposited on the plate in accordance with the bias supplied to the X and Y conductors.
There is described in that patent an electrophoretic dispersion suitable for operation with the display as well as techniques for fabricating the display. Hence, in this manner the displays can be fabricated to contain large effective display surfaces while being relatively thin and which are capable of high resolution and relatively low power. As indicated, the above-noted patent and others include information concerning the fabrication, operation and resolution of such displays.
See also U.S. Pat. No. 4,772,820 entitled "Monolithic Flat Panel Display Apparatus" issued on Sept. 20, 1988 to Frank J. DiSanto et al. and assigned to the assignee herein. This patent shows an electrophoretic display as well as methods for fabrication and operating such a display.
See also U.S. Pat. No. 4,742,345 entitled "Electrophoretic Display Panel Apparatus And Methods Therefor" by Frank J. DiSanto et al. and assigned to the assignee herein. This patent shows such a display having improved alignment and contrast characteristics and structure and methods for aligning and operating such a display.
See also U.S. Pat. No. 4,746,917 entitled "Methods And Apparatus For Operating An Electrophoretic Display Between A Display And A Non-Display Mode" issued on May 24, 1988 to Frank J. DiSanto et al. and assigned to the assignee herein. This patent shows and describes a power supply circuit for operating such a display between a display and a non-display mode.
As one can ascertain from the prior art, the electrophoretic display has been thoroughly investigated and essentially it is a continuing object to provide more reliable operation as well as to provide displays which permit greater control of the image producing pigment particles as propagating within the display.
The electrophoretic effect is associated with working fluids which includes a dispersion of electrophoretic particles. These particles may be fabricated from an opaque dielectric material or a pigment which particles are suspended in a colored non-conducting suspension medium. The particles preferably are uniformly distributed throughout the suspension medium and the contrast between the particles and the suspension medium is the mechanism which enables one to formulate an image.
When the composite material is subjected to an electric field, the particles are caused to move electrophoretically in the direction of either the cathode or the anode. These particles are deposited upon the respective structure to cause that structure to assume the color of the particle which, for example, may be grey, white or some other color depending upon the pigment utilized. Hence, as one can ascertain, by selectively moving the particles one can produce images based on the migration and orientation of the particles with respect to a charged surface. As indicated, this effect is well known as for example ascertained by the above-noted prior art and many of the references cited against such prior art.
As one will immediately understand, it is a major object in all such displays to produce a reliable display as well as to provide a uniform and rapid movement of the particles. In prior art displays, extreme difficulty was experienced when attempting to move the particles at high speeds and to further control the particles so that a uniform image is displayed. It was a further difficulty to utilize lighting as back lighting with such a display due to the fact that the anode electrode, which is a planar electrode, is not totally transparent but essentially is semi-transparent and hence any attempts to back light the displays of the prior art were difficult to accommodate.
It is an object of the present invention to provide a mesh electrode which mesh electrode provides greater control of the pigment particles and therefore provides a display which is more reliable and easier controlled than those of the prior art.
It is a further object to provide an electrophoretic display having a mesh electrode to enable back lighting of the display and hence overcoming many of the prior art problems.